Laser is used for various kinds of therapy. For example, laser therapy apparatuses are used in photodynamic therapy (hereinafter abbreviated as “PDT”).
PDT is a localized therapy which utilizes a photochemical reaction based on a photosensitive substance which abundantly accumulates in cancer cells as well as laser light irradiation. Specifically, in this therapy, a photosensitive substance (e.g., talaporfin sodium) is administered in vivo, and the cancer cells in which the photosensitive substance has accumulated are irradiated with laser light of an excitation wavelength which is specific to that photosensitive substance, thus generating singlet oxygens from the photosensitive substance, and allowing these singlet oxygens to destroy the cancer cells.
For example, a laser therapy apparatus for use in PDT is proposed in Patent Document 1.